Physical Science

1. GREEK VIEWS OF MATTER, MOTION, AND THE UNIVERSE.
Matter: Most of the Greek Philosophers thought that matter was composed of some set of basic "elements", for
example, the familiar Earth, Air, Fire, and Water. Some philosophers proposed the presence of a fifth element,
known as quintessence or “aether”.
Motion: Among the first phenomena considered by the curious Greeks was motion. One might initially suspect
that motion is an attribute of life; after all, men and cats move freely but stones do not. A stone can be made to
move, to be sure, but usually through the impulse given it by a living thing.
Universe: Greek philosophers estimated the distance to the Moon, and even tried to calculate the size of the
entire universe. They believed it was finite. The outer sphere of the stars carried them on their nightly course
around the Earth. The natural place for earthy material was down at the center of the universe.
2. COMPETING MODELS OF THE UNIVERSE BY EUDOXUS, ARISTOTLE, ARISTARCHUS,

PTOLEMY.
The Golden age of early astronomy began in Ancient Greece around 600 B.C. The Greeks were able to
explain natural phenomena from their observations of the world.
1. Aristotle (384-322 B.C) concluded that the earth is spherical because of the curved shadow it casts on the
moon during eclipses.
2. Eratosthenes measures the circumference of the earth using principles of geometry.
3. Aristarchus (312-230 B.C) the first Greek to speculate about a Heliocentric (sun-centered) universe through
his geometric calculations of the size and distances of the moon and sun.
4. Ptolemy (A.D 141) includes the models of the universe from the motion of celestial bodies. In his work
Almagest, the planets move around the Earth in perfect circular orbits. He was able to develop such good
models explaining the movement of celestial bodies by using circles and remaining to an Earth-centered
universe ideology.
3. COPERNICUS, BRAHE, AND KEPLER.

Copernicus:
 Nicolaus Copernicus (1473–1543) was a mathematician and astronomer who proposed that the sun
was stationary in the center of the universe and the earth revolved around it.
 Nicolaus Copernicus was a Polish astronomer and mathematician known as the father of modern
astronomy. He was the first European scientist to propose that Earth and other planets revolve around
the sun, the heliocentric theory of the solar system.
 Copernicus adopted a heliocentric view because it better explained the motions of the heavens
mathematically. This view had the Earth and other planets moving in circles around the fixed Sun.
Brahe:
 Tycho Brahe was a Danish astronomer who is best known for the astronomical observations which led
Kepler to his theories of the Solar system.
 Brahe's Model of the Cosmos
In Brahe's model, all of the planets orbited the sun, and the sun and the moon orbited the Earth.
Keeping with his observations of the new star and the comet, his model allowed the path of the planet
Mars to cross through the path of the sun.
 Brahe showed irregularities in the Moon's orbit and discovered a new star in the Cassiopeia
formation. Brahe invented many instruments such as the Tyconian Quadrant which were widely copied
and led to the invention of improved observational equipment.
 Brahe made careful observations of a comet in 1577. By measuring the parallax for the comet, he was
able to show that the comet was further away than the Moon.
 One of the major contributions of Tycho Brahe was the development of the mathematical and
astronomical theories of astronomy, including an accurate system of timekeeping.
Kepler:
 Johannes Kepler was a German mathematician and astronomer who discovered that the Earth and
planets travel about the sun in elliptical orbits. He gave three fundamental laws of planetary motion.
He also did important work in optics and geometry.
 Kepler's Laws of Planetary Motion
They describe how (1) planets move in elliptical orbits with the Sun as a focus, (2) a planet covers the
same area of space in the same amount of time no matter where it is in its orbit, and (3) a planet's orbital
period is proportional to the size of its orbit (its semi-major axis).
 Kepler was formally schooled in Latin, the language of academics, lawyers and churchmen throughout
Europe. Hoping to become a Protestant minister he attended the Protestant Seminary of Maulbronn.
 There are actually three, Kepler's laws that is, of planetary motion: 1) every planet's orbit is an ellipse
with the Sun at a focus; 2) a line joining the Sun and a planet sweeps out equal areas in equal times; and
3) the square of a planet's orbital period is proportional to the cube of the semi-major axis
4. EVIDENCE THAT THE EARTH IS NOT THE CENTER OF THE UNIVERSE .

 On the 27th of February, four minutes after the first hour, the stars appeared in this
configuration: The easternmost was ten minutes from Jupiter; the next, thirty seconds. ' Galileo
had seen three of Jupiter'''s four largest moons, effectively proving the Earth was not the center
of the universe.
 astronomer Nicolaus Copernicus
 Galileo'''s drawings upended the world view that had lasted for at least two millennia. In 1543,
Polish astronomer Nicolaus Copernicus questioned the idea that the Earth was the center of the
universe, but couldn'''t provide proof. Galileo did. The universe was changing and this book was
the agent of that change.
 Hubble discovered that the galaxies are moving away from us with a velocity proportional to
their distance. Every point in the universe is expanding from every other point at a constant
rate. There is no expansion from a particular point. We know about this expansion due to the
red-shift of galaxies.

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1. GREEK VIEWS OF MATTER, MOTION, AND THE UNIVERSE.

2. COMPETING MODELS OF THE UNIVERSE BY EUDOXUS, ARISTOTLE, ARISTARCHUS,

2. Eratosthenes measures the circumference of the earth using principles of geometry.

3. COPERNICUS, BRAHE, AND KEPLER.

4. EVIDENCE THAT THE EARTH IS NOT THE CENTER OF THE UNIVERSE .

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